1. Field of the Invention
This invention relates to substituted 4-oxg-napthyridine-3-carboxamides and, in particular, such compounds which selectively bind to GABAa receptors. This invention also relates to pharmaceutical compositions comprising such compounds and to the use of such compounds in enhancing alertness and treating anxiety, overdoses of benzodiazepine-type drugs, Down Syndrome, and sleep, seizure and cognitive disorders.
2. Description of the Related Art
xcex3-Aminobutyric acid (GABA) is regarded as one of the major inhibitory amino acid transmitters in the mammalian brain. Over 40 years have elapsed since its presence in the brain was demonstrated (Roberts and Frankel, J. Biol. Chem 187: 55-63, 1950; Udenfriend, J. Biol. Chem. 187: 65-69, 1950). Since that time, an enormous amount of effort has been devoted to implicating GABA in the etiology of seizure disorders, sleep, anxiety and cognition (Tallman and Gallager, Ann. Rev. Neuroscience 8: 21-44, 1985). Widely, although unequally, distributed through the mammalian brain, GABA is said to be a transmitter at approximately 30% of the synapses in the brain. GABA mediates many of its actions through a complex of proteins localized both on cell bodies and nerve endings; these are called GABAa receptors. Postsynaptic responses to GABA are mediated through alterations in chloride conductance that generally, although not invariably, lead to hyperpolarization of the cell. Drugs that interact at the GABAa receptor can possess a spectrum of pharmacological activities depending on their abilities to modify the actions of GABA.
The 1,4-Benzodiazepines, such as diazepam, continue to be among the most widely used drugs in the world as anxiolytics, sedative-hypnotics, muscle relaxants, and anticonvulsants. A number of these compounds are extremely potent drugs; such potency indicates a site of action with a high affinity and specificity for individual receptors. Early electro-physiological studies indicated that a major action of benzodiazepines was enhancement of GABAergic inhibition. Presently, those compounds possessing activity similar to the benzodiazepines are called agonists. Compounds possessing activity opposite to benzodiazepines are called inverse agonists, and the compounds blocking both types of activity have been termed antagonists.
The GABAa receptor subunits have been cloned from bovine and human cDNA libraries (Schoenfield et al., 1988; Duman et al., 1989). A number of distinct cDNAs were identified as subunits of the GABAa receptor complex by cloning and expression. These are categorized into xcex1, xcex2, xcex3, xcex4, xcex5, and provide a molecular basis for the GABAa receptor heterogeneity and distinctive regional pharmacology (Shivvers et al., 1980; Levitan et al., 1989). The xcex3 subunit appears to enable drugs like benzodiazepines to modify the GABA responses (Pritchett et al., 1989). The presence of low Hill coefficients in the binding of ligands to the GABAa receptor indicates unique profiles of subtype specific pharmacological action.
With the discovery of the xe2x80x9creceptorxe2x80x9d for the benzodiazepines and the subsequent definition of the nature of the interaction between GABA and the benzodiazepines, it appears that the behaviorally important interactions of the benzodiazepines with different neurotransmitter systems are due in a large part to the enhanced ability of GABA itself to modify these systems. Each modified system, in turn, may be associated with the expression of a behavior. Depending on the mode of interaction, these compounds are capable of producing a spectrum of activities (either sedative, anxiolytic, and anticonvulsant, or wakefulness, seizures, and anxiety).
Various 1,4-dihydro-4-oxo-1,5-naphthyridine-3-carboxylic acids and esters have been disclosed. See, for example, Eur. J. Med. Chem.-Chim. Ther. (1977), 12 (6), 549-55.
Polish Patent No. 125299 discloses compounds of the formula: 
wherein N denotes a ring nitrogen in the 5- or 6-position, and R is CO2H or CO2Et.
Several 1,4-dihydro-4-oxo-1,5-napthyridine-3-carboxamide derivatives of penicillin said to possess antibacterial activity have been disclosed. For example, German Patent. No. DD 279887 discloses a compound of the formula 
Japanese Patent No. 72-45118 discloses ampicillin derivatives of 1,4-dihydro-4-oxo-3-naphthyridines.
This invention provides novel compounds of Formula I which interact with a GABAa binding site, the benzodiazepine receptor.
The invention provides pharmaceutical compositions comprising compounds of Formula I. The invention also provides compounds useful in the diagnosis and treatment of anxiety, Down Syndrome, sleep, cognitive and seizure disorders, and overdose with benzodiazepine drugs and for enhancement of alertness. Accordingly, a broad embodiment of the invention is directed to compounds of Formula I: 
wherein:
X is hydrogen, halogen, xe2x80x94OR1, C1-C6 alkyl optionally substituted with up to three groups selected independently from halogen and hydroxy, or xe2x80x94NR2R3;
X is phenyl, naphthyl, 1-(5,6,7,8-tetrahydro)naphthyl or 4-(1,2-dihydro)indenyl, pyridinyl, pyrimidyl, isoquinolinyl, 1,2,3,4-tetrahydroisoquinolinyl, benzofuranyl, benzothienyl, each of which is optionally substituted with up to three groups selected from halogen, C1-C5 alkyl, C1-C4 alkoxy, C1-C5 alkylthio, hydroxy, amino, mono or di(C1-C6)alkylamino, cyano, nitro, trifluoromethyl or trifluoromethoxy; or
X represents a carbocyclic group (xe2x80x9cthe X carbocyclic groupxe2x80x9d) containing from 3-7 members, up to two of which members are optionally hetero atoms selected from oxygen and nitrogen, where the X carbocyclic group is optionally substituted with one or more groups elected from halogen, alkoxy, mono- or dialkylamino, sulfonamide, azacycloalkyl, cycloalkylthio, alkylthio, phenylthio, or a heterocyclic group;
Y is lower alkyl having 1-8 carbon atoms optionally substituted with up to two groups selected from halogen, alkoxy, mono- or dialkylamino, sulfonamide, azacycloalkyl, cycloalkylthio, alkylthio, phenylthio, a heterocyclic group, xe2x80x94OR4, xe2x80x94NR5R6, SR7, or aryl; or
Y is a carbocyclic group (xe2x80x9cthe Y carbocyclic groupxe2x80x9d) having from 3-7 members atoms, where up to three of which members are optionally hetero atoms selected from oxygen and nitrogen and where any member of the Y carbocyclic group is optionally substituted with halogen, xe2x80x94OR4, xe2x80x94NR5R6, SR7, aryl or a heterocyclic group;
R1 is hydrogen, lower alkyl having 1-6 carbon atoms, or cycloalkyl having 3-7 carbon atoms, where each alkyl may be optionally substituted with xe2x80x94OR4, or xe2x80x94NR5R6;
R2 and R3 are the same or different and represent
hydrogen, lower alkyl optionally mono- or disubstituted with alkoxy, aryl, halogen, or mono- or di-lower alkyl;
aryl or aryl(C1-C6)alkyl where each aryl is optionally substituted with up to three groups selected from halogen, hydroxy, C1-C6 alkyl, C1-C6 alkoxy, or mono- or di(C1-C6)alkylamino;
cycloalkyl having 3-7 carbon atoms optionally mono or disubstituted with halogen, alkoxy, or mono- or di-lower alkyl; or
xe2x80x94SO2R8;
R4 is as defined for R1;
R5 and R6 carry the same definitions as R2 and R3, respectively;
R7 is hydrogen, lower alkyl having 1-6 carbon atoms, or cycloalkyl having 3-7 carbon atoms; and
R8 is lower alkyl having 1-6 carbon atoms, cycloalkyl having 3-7 carbon atoms, or optionally substituted phenyl.
These compounds are highly selective agonists, antagonists or inverse agonists for GABAa brain receptors or prodrugs of agonists, antagonists or inverse agonists for GABAa brain receptors. These compounds are useful in the diagnosis and treatment of anxiety, Down Syndrome, sleep, cognitive and seizure disorders, and overdose with benzodiazepine drugs and for enhancement of alertness.
The novel compounds encompassed by the invention can be described by the general Formula I set forth above.
In Formula I above, xe2x80x94NR2R3 can also represent a heterocyclic group such as, for example, piperidine in the case where R2 and R3 together form a C5-alkylene group. Further, R2 and R3 together may represent an alkylene or alkenylene group optionally containing up to two heteroatoms selected from nitrogen and oxygen. The resulting groups include imidazolyl, pyrrolidinyl, morpholinyl, piperazinyl, and piperidinyl.
Similarly, the xe2x80x94NR5R6 group in Formula I above can also represent a heterocyclic group such as, for example, piperidine in the case where R5 and R6 together form a C5-alkylene group. Further, R5 and R6 together may represent an alkylene or alkenylene group optionally containing up to two heteroatoms selected from nitrogen and oxygen. The resulting groups include imidazolyl, pyrrolidinyl, morpholinyl, piperazinyl, and piperidinyl.
Preferred compounds of Formula I are those where X represents (C1-C6)alkoxy, more preferably (C1-C3)alkoxy. Particularly preferred compounds of Formula I include methoxy or ethoxy as the X group.
Still other preferred compounds of Formula I include those where the Y is lower alkyl, e.g., methyl or ethyl, substituted with phenyl, pyridyl, or pyrimidinyl. A more preferred Y group is benzyl optionally substituted with halogen, (C1-C6)alkyl, (C1-C6)alkoxy, amino, or mono- or di(C1-C6)alkyl.
Where R2 and R3 in Formula I represent optionally substituted aryl or aryl(C1-C6)alkyl, the aryl group is preferably phenyl, pyridyl, or pyrimidinyl and the alkyl groups are preferably methyl and ethyl. More preferred are benzyl and phenyl. Particularly preferred is benzyl.
Where X is optionally substituted C1-C6 alkyl, the alkyl group is preferably optionally substituted methyl, ethyl, or propyl. More preferred are perhalomethyl and trihaloethyl. Preferred halogens are fluorine. Particularly preferred is 2,2,2-trifluoroethyl.
X in Formula I may be an optionally substituted phenyl, naphthyl, 1-(5,6,7,8-tetrahydro)naphthyl, 4-(1,2-dihydro)indenyl, pyridinyl, pyrimidyl, isoquinolinyl, benzofuranyl, or benzothienyl group, or preferably a 1,2,3,4-tetrahydroisoquinolinyl group.
In addition to the compounds of Formula I, the invention encompasses compounds of Formula IA 
wherein:
X is
(i) hydrogen, halogen, mono- or dialkylamino, alkoxy,
(ii) a group of the formula: 
where G is lower alkylene having 1-6 carbon atoms, or a cyclic group of the formula 
where n is 0, 1, or 2, and m is an integer of from 1 to 5, with the proviso that the sum of n+m is not less than 1 or greater than 5; and
R1 is hydrogen, lower alkyl, or (C3-C7)cycloalkyl, where the alkyl or cycloalkyl is optionally substituted with halogen, lower alkoxy, or mono- or di(C1-C6)alkylamino;
(iii) a group of the formula: 
xe2x80x83where
G is as defined above for ii; and
R2 and R3 independently represent hydrogen, lower alkyl having 1-6 carbon atoms, cycloalkyl having 3-7 carbon atoms, xe2x80x94SO2R8 where R8 is (C1-C6)alkyl, (C3-C7)cycloalkyl, or optionally substituted phenyl, or
R2 and R3 together with the nitrogen atom to which they are attached form a heterocyclic moiety such as imidazolyl, pyrrolidinyl, morpholinyl, piperazinyl, or piperidinyl;
(iv) a group of the formula: 
xe2x80x83where
R2 is as defined above for iii;
R4 is hydrogen, lower alkyl having 1-6 carbon atoms, or cycloalkyl having 3-7 carbon atoms, and may be optionally substituted with one or more (C1-C6)alkoxy or mono- or di(C1-C6)alkylamino groups; and
G is as defined above for ii;
(v) a group of the formula: 
xe2x80x83where
R2 and G are as defined above for iv and ii, respectively, and
R5 and R6 independently represent hydrogen, lower alkyl having 1-6 carbon atoms, cycloalkyl having 3-7 carbon atoms, xe2x80x94SO2R8 where R8 is (C1-C6)alkyl, (C3-C7)cycloalkyl, or optionally substituted phenyl, or
R5 and R6 together with the nitrogen atom to which they are attached form a heterocyclic moiety such as imidazolyl, pyrrolidinyl, morpholinyl, piperazinyl, or piperidinyl;
(vi) a group of the formula: 
where G is as defined above for ii; or
(vii) a group of the formula: 
where each G is as defined above for ii; and
Y is
(viii) lower alkyl having 1-8 carbon atoms or cycloalkyl having 3-7 carbon atoms, any of which may be optionally substituted with one or more hydroxy, halogen, (C1-C6)alkoxy, alkoxyalkoxy where each alkoxy is (C1-C6)alkoxy, (C1-C6)alkylthio, (C3-C7)cycloalkylthio, aryl, heteroaryl, or mono- or di(C1-C6)alkylamino groups;
(ix) a group of the formula: 
where K is lower alkylene having 1-6 carbon atoms optionally substituted with (C1-C6)alkyl or alkylene, or a cyclic group of the formula 
where Kxe2x80x2 independently represents hydrogen or (C1-C6) alkyl or alkylene, n is 0, 1, or 2, and m is an integer of from 1 to 5, with the proviso that the sum of n+m is not less than 1 or greater than 5; and
R9 is hydrogen, lower alkyl, or (C3-C7)cycloalkyl, where the alkyl or cycloalkyl is optionally substituted with halogen, lower alkoxy, or mono- or dialkylamino;
(x) a group of the formula: 
where K is defined as above in ix;
(xi) a group of the formula: 
xe2x80x83where
K is as defined above for ix, and
R13 is hydrogen, lower alkyl having 1-6 carbon atoms, or cycloalkyl having 3-7 carbon atoms, where the alkyl and cycloalkyl groups are optionally substituted with one or more (C1-C6)alkoxy or mono- or di(C1-C6)alkylamino groups; and
(xii) a group of the formula: 
xe2x80x83where
K is as defined above for ix, and
R7 is hydrogen, lower alkyl having 1-6 carbon atoms, or cycloalkyl having 3-7 carbon atoms; and
(xiii) a group of the formula: 
xe2x80x83where
K is as defined above for ix; and
R14 and R15 independently represent hydrogen, lower alkyl having 1-6 carbon atoms, cycloalkyl having 3-7 carbon atoms, xe2x80x94SO2R8 where R8 is as defined above, or
R14 and R15 together with the nitrogen atom to which they are attached form a heterocyclic moiety such as imidazolyl, pyrrolidinyl, morpholinyl, piperazinyl, or piperidinyl;
(xiv) a group of the formula: 
where K and R15 are as defined above in ix and xii, respectively;
(xv) a group of the formula: 
xe2x80x83where
K is as defined above for ix;
R10 and R10xe2x80x2 are the same or different and are selected from hydrogen, (1-C6)alkyl, halogen, hydroxy, lower alkoxy having 1-6 carbon atoms, or cycloalkoxy having 3-7 carbon atoms;
R11, R11xe2x80x2, and R12 are the same or different and are selected from hydrogen, C1-C6 alkyl, halogen, hydroxy, xe2x80x94OR4, xe2x80x94CR7(R9) NR5R6, xe2x80x94CR9(R16)OR4,
or R11 and R12 taken together with the atoms to which they are attached form a (hetero)cyclic ring; and
R16 is hydrogen, lower alkyl having 1-6 carbon atoms, or cycloalkyl having 3-7 carbon atoms;
(xvi) a group of the formula: 
where K is as defined above for ix; and W is heteroaryl;
(xvii) a group of the formula: 
xe2x80x83where
K is as defined above for ix; R10 and R11 are as defined above for xv, and
R17 is hydrogen, lower alkyl, or (C3-C7)cycloalkyl, where the alkyl or cycloalkyl is optionally substituted with halogen, lower alkoxy, or mono- or di(C1-C6)alkylamino;
(xviii) a group of the formula: 
where K, R10, R12, and R17 are as defined above;
(xix) a group of the formula: 
where each K is independently as defined above for ix and R10 is defined above;
(xx) a group of the formula: 
where K, R10, R11, R14, and R15 are as defined above;
(xxi) a group of the formula: 
where K, R10, R12, R14, and R15 are as defined above;
(xxii) pyrimidinyl(C1-C6)alkyl or pyridyl(C1-C6)alkyl; or
(xxiii) a group of the formula: 
where R18 represents hydrogen, amino, mono-, or di(C1-C6)alkylamino, or C1-C6 alkyl optionally substituted with a R19 where R18 represents: 
xe2x80x83where
V and Vxe2x80x2 are independently CH or nitrogen;
Axe2x80x3 is C1-C6 alkylene; and
R20 is phenyl, pyridyl, or pyrimidinyl, each of which is optionally mono-, di-, or trisubstituted independently with halogen, hydroxy, C1-C6 alkoxy, amino, or mono- or di(C1-C6)alkylamino.
Preferred pyrimidinyl(C1-C6)alkyl Y groups are 2- and 4-pyrimidinylmethyl. Preferred pyridyl(C1-C6)alkyl Y groups are 2- and 4-pyridylmethyl.
Preferred benzyl Y groups are those where R18 is amino or a substituted methyl or ethyl group. More preferred R18 substituents are piperazin-1-yl or piperidin-1-yl substituted at the 4-position with a halogenated benzyl group. Particularly preferred benzyl Y groups are 4-[1-[4-(4-Fluorobenzyl)piperazinyl]methyl]benzyl and 4-[1-[4-(4-Fluorobenzyl)piperidinyl]methyl]benzyl.
Preferred xe2x80x9cXxe2x80x9d groups in Formula IA are various quinolinyl, isoquinolinyl, tetrahydroquinolinyl or tetrahydroisoquinolinyl groups, e.g., groups of the formulas: 
The following formulae are preferred embodiments of the invention: 
wherein Y is defined above. 
wherein Z represents halogen and Y is as defined above. 
wherein R1 and Y are defined above. 
wherein R2, R3, and Y are defined above. 
wherein R2, R8, and Y are defined above. 
wherein R1, G and Y are defined above. 
wherein R2, R3, G, and Y are defined above. 
wherein R2, R4, G, and Y are defined above. 
wherein R2, R5, R6, G, and Y are defined above. 
wherein G and Y are defined above. 
wherein R2, G, and Y are defined above. 
wherein X is defined above and U is (C1-C6)lower alkyl or (C1-C6)cycloalkyl. 
wherein X, K, and R1 are defined above. 
wherein X and K are defined above. 
wherein X, K, and R4 are defined above. 
wherein X, K, and R7 are defined above. 
wherein X, K, R14, and R15 are defined above. 
wherein X, K, and R15 are defined above. 
wherein:
R10, R10xe2x80x2 are the same or different and may be selected from hydrogen, (C1-C6)alkyl, halogen, hydroxy, lower alkoxy having 1-6 carbon atoms, or cycloalkoxy having 3-7 carbon atoms;
R11, R11xe2x80x2, and R12 are the same or different and may be selected from hydrogen, (C1-C6)alkyl, halogen, hydroxy, xe2x80x94OR4, xe2x80x94CR7(R9)NR5R6, xe2x80x94CR7(R9)OR4; or
R11 and R12 taken together with the atoms to which they are attached form a (hetero)cyclic ring; and
R9is as defined above. 
wherein
X and K are defined above; and
W is heteroaryl. 
wherein X, K, R1, R10, and R11 are defined above. 
wherein X, K, R1, R10, and R12 are defined above. 
wherein X, K, and R10 are defined above. 
wherein X, K, R14, R15, R10, and R11 are defined above. 
Preferred compounds of the invention are encompassed by the following formulae: 
where
A is C1-C6 alkylene;
Ra is phenyl optionally mono-, di-, or trisubstituted with halogen, lower alkyl, lower alkoxy, or mono- or di-C1-C6 alkylamino, or mono- or di-C1-C6 alkylamino lower alkyl; and
Rb is lower alkyl or lower cycloalkyl.
More preferred compounds of Formula XXVII are those where A is methylene, Ra is phenyl optionally substituted with methyl or ethyl, and Rb is lower alkyl. Particularly preferred compounds of Formula XXVII are those where A is methylene, Ra is phenyl and Rb is C1-C3 alkyl. 
wherein
A is C1-C6 alkylene;
Ra and Raxe2x80x2 are independently phenyl groups optionally mono-, di-, or trisubstituted with halogen, lower alkyl, lower alkoxy, or mono- or di-C1-C6 alkylamino, or mono- or di-C1-C6 alkylamino lower alkyl; and
Rc is hydrogen or lower alkyl.
More preferred compounds. of Formula XXVIII are those where A is methylene, Ra and Raxe2x80x2 are independently phenyl optionally substituted with methyl or ethyl, and Rc is lower alkyl. Particularly preferred compounds of Formula XXVII are those where A is methylene, Ra is phenyl substituted in the para position with lower alkyl, Raxe2x80x2 is phenyl, and Rc is C1-C3 alkyl. 
wherein
A is C1-C6 alkylene;
Rd and Re are independently lower alkyl groups.
More preferred compounds of Formula XXIX are those where A is C2-C4 alkylene. Particularly preferred compounds of Formula XXIX are those where A is C2-C4 alkylene, Rd is C1-C3 alkyl, and Re is C2-C4 alkyl. 
wherein
A is C1-C6 alkylene;
Rd is lower alkyl; and
Rf is a group of the formula: 
xe2x80x83where
E is oxygen or nitrogen; and
M is C1-C3 alkylene or nitrogen.
More preferred compounds of Formula XXX are those where A is C1xe2x80x94C3 alkylene. Still more preferred compounds of Formula XXX are those where A is C2-C4 alkylene, Rd is C1-C3 alkyl, and Re is C2-C4 alkyl. Particularly preferred compounds of Formula XXX are those where A is C2-C4 alkylene, Rd is C1-C3 alkyl, Re is C2-C4 alkyl, and E is nitrogen and M is methylene, E is oxygen and M is methylene or ethylene, or E and M are both nitrogen.
Other preferred compounds of Formula XXX are those where Rf is furanyl, tetrahydrofuranyl, or imidazolyl. 
wherein
A is C1-C6 alkylene;
Rd is lower alkyl optionally substituted with amino or mono- or di(C1-C6)alkylamino; and
Raxe2x80x2 is phenyl optionally mono-, di-, or trisubstituted with halogen, lower alkyl, lower alkoxy, or mono- or di-C1-C6 alkylamino, or mono- or di-C1-C6 alkylamino lower alkyl.
More preferred compounds of Formula XXXI are those where A is C1-C3 alkylene, Raxe2x80x2 is phenyl optionally substituted with methyl or ethyl, and Rd is C1-C3 alkyl. Still mere preferred compounds of Formula XXXI are where A is methylene, Raxe2x80x2 is phenyl optionally substituted with methyl or ethyl, and Rd is C3-C6 alkyl. Particularly preferred compounds of Formula XXXI are sodium, potassium, or ammonium salts of the corresponding parent compound.
Other preferred compounds of Formula XXXI are those where Raxe2x80x2 is phenyl substituted with mono- or di-(C1-C6)alkylamino lower alkyl. 
wherein
A is C1-C6 alkylene;
Rd is lower alkyl; and
Raxe2x80x3 is phenyl, pyridyl, imidazolyl, pyrimidinyl, or pyrrolyl, each of which is optionally substituted with up to two groups selected from halogen, lower alkyl, lower alkoxy, mono- or di(C1-C6)alkylamino, or mono- or di-C1-C6 alkylamino lower alkyl.
More preferred compounds of Formula XXXIa are those where Raxe2x80x3 is imidazolyl and Rd is C1-C3 alkyl. Still more preferred compounds of Formula XXXI are where A is methylene, Raxe2x80x3 is imidazolyl, and Rd is C3-C6 alkyl. 
wherein
A is C1-C5 alkylene; and
Rd and Re are independently lower alkyl groups.
More preferred compounds of Formula XXXII are those where A is C1-C3 alkylene. Particularly preferred compounds of Formula XXXII are those where A is C1-C3 alkylene, Rd is C1-C3 alkyl, and Re is C1-C3 alkyl. 
wherein
D is nitrogen or CH;
Dxe2x80x2 is nitrogen or oxygen;
A is C1-C6 alkylene; and
Raxe2x80x2 is phenyl, pyridyl, or thiazolyl, each of which is optionally mono-, di-, or trisubstituted with halogen, lower alkyl, lower alkoxy, or mono- or di-C1-C6 alkylamino, or mono- or di-C1-C6 alkylamino lower alkyl.
More preferred compounds of Formula XXXIII are those where A is C1-C3 alkylene, Raxe2x80x2 is phenyl optionally substituted with lower alkyl or halogen, and D is nitrogen. Still more preferred compounds of Formula XXXIII are where A is methylene, Raxe2x80x2 is phenyl optionally substituted, with lower alkyl or halogen, D is nitrogen, and Dxe2x80x2 is oxygen. 
wherein
A is C1xe2x80x94C6 alkylene; and
Raxe2x80x2 is hydrogen;
Raxe2x80x2 is thienyl or phenyl, each of which is optionally mono-, di-, or trisubstituted with halogen, lower alkyl, lower alkoxy, or mono- or di-C1-C6 alkylamino, or mono- or di-C1-C6 alkylamino lower alkyl.
More preferred compounds of Formula XXXIV are those where A is C1-C3 alkylene, and Raxe2x80x2 is phenyl optionally substituted with lower alkyl or halogen. Still more preferred compounds of Formula XXXIV are where A is methylene, Raxe2x80x2 is phenyl optionally substituted with lower alkyl, lower alkoxy or halogen. 
wherein
A is C1-C6 alkylene; and
Rd is lower alkyl;
Axe2x80x2 represents oxygen or methylene; and
r is an integer of from 1-3.
More preferred compounds of Formula XXXV are those where A is C1-C3 alkylene. Particularly preferred compounds of Formula XXXV are those where A is C1-C3 alkylene, and Rd is C1-C3 alkyl. 
wherein
A is C1-C6 alkylene; and
Rh and Rhxe2x80x2 are independently hydrogen or lower alkyl, where each alkyl is optionally substituted with lower alkoxy;
Axe2x80x2 represents oxygen or methylene; and
r is an integer of from 1-3.
More preferred compounds of Formula XXXVa are those where A is C1-C3 alkylene. Particularly preferred compounds of Formula XXXV are those where A is C1-C3 alkylene, and Rh is C1-C3 alkyl. 
wherein
A is C1-C6 alkylene;
Rg is lower alkoxy lower alkyl; and
Raxe2x80x2 is phenyl optionally mono-, di-, or trisubstituted with halogen, lower alkyl, lower alkoxy, or mono- or di-C1-C6 alkylamino, or mono- or di-C1-C6 alkylamino lower alkyl. 
wherein
Rj is halogen or lower alkoxy; and
Rk is lower alkyl or cycloalkyl each of which is optionally substituted with hydroxy, lower alkyl, or lower alkoxy; or
Rk is phenyl (C1-C6) alkyl where the phenyl group is optionally mono-, di-, or trisubstituted with halogen, lower alkyl, lower alkoxy, or mono- or di-C1-C6 alkylamino, or mono- or di-C1-C6 alkylamino lower alkyl. 
wherein
A is C1-C6 alkylene;
Rl is lower alkoxy, benzyloxy, lower alkoxy lower alkoxy, amino, or mono- or di-(C1-C6)alkylamino; and
Rm is pyranyl, dihydropyranyl, tetrahydropyranyl, or hexahydropyranyl, pyridine, dihydropyridine, tetrahydropyridine, or piperidine.
Preferred compounds of Formula XXXVIII are those where Rl is lower alkoxy and Rm is tetrahydropyranyl. 
wherein
A is C1-C6 alkylene;
Rn is lower alkoxy, lower alkoxy lower alkoxy, benzyl, or a group of the formula: 
xe2x80x83where
D is nitrogen or CH; and
Dxe2x80x2 is nitrogen or oxygen; and
Ro is pyranyl, 2- or 3-thienyl; or
Ro is 2-, 4-, or 5-thiazolyl or 2-, 4-, or 5-imidazolyl, each of which may be optionally substituted with lower alkyl.
Preferred compounds of Formula XXXIX are those where 
wherein
A is C1-C6 alkylene;
Rh and Rhxe2x80x2 are independently hydrogen or lower alkyl, where each lower alkyl is optionally substituted with lower alkoxy; and
Raxe2x80x2 is phenyl optionally mono-, di-, or trisubstituted with halogen, lower alkyl, lower alkoxy, or mono- or di-C1-C6 alkylamino, or mono- or di-C1-C6 alkylamino lower alkyl; or
Raxe2x80x2 is thienyl optionally substituted with lower alkyl. 
wherein
A is C1-C6 alkylene;
D is nitrogen or CH;
Dxe2x80x2 is nitrogen or oxygen; and
Rp is lower alkyl or lower alkyl optionally substituted with lower alkoxy. 
wherein
A is C1-C6 alkylene;
X is defined as above for Formula I; and
R18 is
(i) amino or mono- or di(C1-C6)alkylamino; or
(ii) lower alkyl optionally substituted with 
xe2x80x83where
V and Vxe2x80x2 are independently CH or nitrogen;
Axe2x80x3 is C1-C6 alkylene; and
R20 is phenyl, pyridyl, or pyrimidinyl, each of which is optionally mono-, di-, or trisubstituted independently with halogen, hydroxy, C1-C6 alkoxy, amino, or mono- or di(C1-C6)alkylamino.
More preferred compounds of Formula XXXXII are those where V is nitrogen and X is C1-C6 alkoxy or C1-C6 alkyl optionally substituted with up to three halogen atoms. Particularly preferred compounds of XXXXII are those where V and Vxe2x80x2 are nitrogen; X is C1-C3 alkoxy or C1-C3 alkyl optionally substituted with up to three halogen atoms; Axe2x80x3 is methylene or ethylene; and R20 is halogenated phenyl. A preferred R20 group is 4-fluorophenyl. Highly preferred compounds of XXXXII are those where X is 2,2,2-trifluoroethyl; V and Vxe2x80x2 are nitrogen; R20 is halogenated phenyl; and A and Axe2x80x2 are methylene or ethylene.
In certain situations, compounds of Formula I may contain one or more asymmetric carbon atoms, so that the compounds can exist in different stereoisomeric forms. These compounds can be, for example, racemates or optically active forms. In these situations, the single enantiomers, i.e., optically active forms, can be obtained by asymmetric synthesis or by resolution of the racemates. Resolution of the racemates can be accomplished, for example, by conventional methods such as crystallization in the presence of a resolving agent, or chromatography, using, for example a chiral HPLC column.
Representative compounds of the present invention, which are encompassed by Formula I, include, but are not limited to the compounds in Table I and their pharmaceutically acceptable acid and base addition salts. In addition, if the compound of the invention is obtained as an acid addition salt, the free base can be obtained by basifying a solution of the acid salt. Conversely, if the product is a free base, an addition salt, particularly a pharmaceutically acceptable addition salt, may be produced by dissolving the free base in a suitable organic solvent and treating the solution with an acid, in accordance with conventional procedures for preparing acid addition salts from base compounds.
Non-toxic pharmaceutical salts include salts, of acids such as hydrochloric, phosphoric, hydrobromic, sulfuric, sulfinic, formic, toluenesulfonic, methanesulfonic, nitric, benzoic, citric, tartaric, maleic, hydroiodic, alkanoic such as acetic, HOOCxe2x80x94(CH2)n-ACOOH where n is 0-4, and the like. Non-toxic pharmaceutical base addition salts include salts of bases such as sodium, potassium, calcium, ammonium, and the like. Those skilled in the art will recognize a wide variety of non-toxic pharmaceutically acceptable addition salts.
The present invention also encompasses the acylated prodrugs of the compounds of Formula I. Those skilled in the art will recognize various synthetic methodologies which may be employed to prepare non-toxic pharmaceutically acceptable addition salts and acylated prodrugs of the compounds encompassed by Formula I.
By lower alkyl in the present invention is meant straight or branched chain alkyl groups having 1-6 carbon atoms, such as, for example, methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, pentyl, 2-pentyl, isopentyl, neopentyl, hexyl, 2-hexyl, 3-hexyl, and 3-methylpentyl.
By cycloalkyl in the present invention is meant cycloalkyl groups having 3-7 atoms such as, for example cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, and cycloheptyl.
By aryl is meant an aromatic carbocyclic group having a single ring (e.g., phenyl), multiple rings (e.g., biphenyl), or multiple condensed rings in which at least one is aromatic, (e.g., 1,2,3,4-tetrahydronaphthyl, naphthyl, anthryl, or phenanthryl), which is optionally mono-, di-, or trisubstituted with, e.g., halogen, lower alkyl, lower alkoxy, lower alkylthio, trifluoromethyl, lower acyloxy, aryl, heteroaryl, and hydroxy.
By lower alkoxy in the present invention is meant straight or branched chain alkoxy groups having 1-6 carbon atoms, such as, for example, methoxy, ethoxy, propoxy, isopropoxy, n-butoxy, sec-butoxy, tert-butoxy, pentoxy, 2-pentyl, isopentoxy, neopentoxy, hexoxy, 2-hexoxy, 3-hexoxy, and 3-methylpentoxy.
By cycloalkoxy in the present invention is meant cycloalkylalkoxy groups having 3-7 carbon atoms where cycloalkyl is defined above.
By halogen in the present invention is meant fluorine, bromine, chlorine, and iodine.
By heteroaryl (aromatic heterocycle) in the present invention is meant one or more aromatic ring systems of 5-, 6-, or 7-membered rings containing at least one and up to four hetero atoms selected from nitrogen, oxygen, or sulfur. Such heteroaryl groups include, for example, thienyl, furanyl, thiazolyl, imidazolyl, (is)oxazolyl, pyridyl, pyrimidinyl, (iso)quinolinyl, naphthyridinyl, benzimidazolyl, and benzoxazolyl.
Specific examples of heteroaryl groups are the following: 
wherein
Q is nitrogen or xe2x80x94CR9;
T is xe2x80x94NR7, oxygen, or sulfur; and
R9, R10, R10xe2x80x2, R11, R11xe2x80x2, R12 are as defined above.
Where Y represents a carbocyclic group, it is attached to the amide nitrogen by a single bond. The result s an amide of the formula: 
where X is defined as above and 
represents the Y carbocyclic group.
Where X is a carbocyclic group, such moiety or group includes both aromatic heterocycles (heteroaryl), unsaturated heterocylic ring systems, and saturated heterocyclic ring systems. Examples of such groups are imidazolyl, pyrrolidinyl, morpholinyl, piperazinyl, or piperidinyl. Preferred X carbocyclic groups are linked to the parent naphthyridine moiety by a nitrogen atom in the X carbocyclic group. Thus, for example, when pyrrolidinyl is the X carbocyclic group, it is preferably a 1-pyrrolidinyl group of the formula: 
Where Y is a carbocyclic group, such moiety or group includes both aromatic heterocycles (heteroaryl groups), unsaturated heterocylic ring systems, and saturated heterocyclic ring systems. Examples of such groups are imidazolyl, pyrrolidinyl, morpholinyl, piperazinyl, or piperidinyl. Preferred Y carbocyclic groups are linked to the parent naphthyridine carboxamide group by a nitrogen atom in the Y carbocyclic group. Thus, for example, when piperidinyl is the Y carbocyclic group, it is preferably a 1-piperidinyl group of the formula: 
By xe2x80x9coptionally substituted phenylxe2x80x9d as used herein is meant phenyl groups that are unsubstituted or substituted with up to 3 groups selected independently from halogen, hydroxy, lower alkyl, lower alkoxy, trifluoromethyl, and mono- or di-lower alkylamino.
Representative compounds of the invention are shown below in Table 1.
The pharmaceutical utility of compounds of this invention is indicated by the following assays for GABAa receptor activity.
Assays are carried out as described in Thomas and Tallman (J. Bio. Chem. 156: 9838-9842, J. Neurosci. 3: 433-440, 1983). Rat cortical tissue is dissected and homogenized in 25 volumes (w/v) of 0.05 M Tris HCl buffer (pH 7.4 at 4xc2x0 C.). The tissue homogenate is centrifuged in the cold (4xc2x0) at 20,000xc3x97g for 20xe2x80x2. The supernatant is decanted and the pellet is rehomogenized in the same volume of buffer and again centrifuged at 20,000xc3x97g. The supernatant is decanted and the pellet is frozen at xe2x88x9220xc2x0 C. overnight. The pellet is then thawed and rehomogenized in 25 volume (original wt/vol) of buffer and the procedure is carried out twice. The pellet is finally resuspended in 50 volumes (w/vol of 0.05 M Tris HCl buffer (pH 7.4 at 40xc2x0 C.).
Incubations contain 100 ml of tissue homogenate, 100 ml of radioligand 0.5 nM (3H-Ro15-1788 [3H-Flumazenil] specific activity 80 Ci/mmol), drug or blocker and buffer to a total volume of 500 ml. Incubations are carried for 30 min at 4xc2x0 C. then are rapidly filtered through GFB filters to separate free and bound ligand. Filters are washed twice with fresh 0.05 M Tris HCl buffer (pH 7.4 at 4xc2x0 C.) and counted in a liquid scintillation counter. 1.0 mM diazepam is added to some tubes to determine nonspecific binding. Data are collected in triplicate determinations, averaged and % inhibition of total specific binding is calculated. Total Specific Binding=Totalxe2x88x92Nonspecific. In some cases, the amounts of unlabeled drugs is varied and total displacement curves of binding are carried out. Data are converted to Ki""s. Compounds of the invention when tested in the assay described above have Ki""s of less than 1 xcexcM.
In addition, the following assay may be used to determine if the compounds of the invention are agonists, antagonists, or inverse agonists, and, therefore, their specific pharmaceutical utility. The following assay can be employed to determine specific GABAa receptor activity.
Assays are carried out as described in White and Gurley (NeuroReport 6: 1313-1316, 1995) and White, Gurley, Hartnett, Stirling, and Gregory (Receptors and Channels 3: 1-5, 1995) with modifications. Xenopus Laevis oocytes are enzymatically isolated and injected with non-polyadenylated cRNA mixed in a ratio of 4:1:4 for human derived xcex1, xcex2, and xcex3 subunits, respectively. For each subunit combination, sufficient message is injected to result in current amplitudes of  greater than 10 nA when 1 xcexcM GABA is applied.
Electrophysiological recordings are carried out using the two electrode voltage-clamp technique at a membrane holding potential of xe2x88x9270 mV.
Compounds are evaluated against a GABA concentration that evokes  less than 10% of the maximal evokable GABA current. Each oocyte is exposed to increasing concentrations of compound in order to evaluate a concentration/effect relationship. Compound efficacy is expressed as a percent-change in current amplitude: 100*((Ic/I)xe2x88x921), where Ic is the GABA evoked current amplitude observed in the presence of compound and I is the GABA evoked current amplitude observed in the absence of compound.
Specificity of a compound for the Ro15-1788 site is determined following completion of the concentration/effect curve. After washing the oocyte sufficiently to remove previously applied compound, the oocyte is exposed to GABA+1 xcexcM Ro15-1788, followed by exposure to GABA+1 xcexcM Ro15-1788+compound. Percent change due to addition of compound is calculated as described above. Any percent change observed in the presence of Ro15-1788 is subtracted from the percent changes in current amplitude observed in the absence of 1 xcexcM Ro15-1788. These net values are used for the calculation of average efficacy and EC50 values.
To evaluate average efficacy and EC50 values, the concentration/effect data are averaged across cells and fit to the logistic equation. Average values are reported as meanxc2x1standard error.
The substituted 4-oxo-napthyridine-3-carboxamides of Formula I and their salts are suitable for the diagnosis and treatment of anxiety, Down Syndrome, sleep, cognitive and seizure disorders, and overdose with benzodiazepine drugs and for enhancement of alertness, both in human and non-human animals and domestic pets, especially dogs and cats and farm animals such as sheep, swine and cattle.
The compounds of general Formula I may be administered orally, topically, parenterally, by inhalation or spray or rectally in dosage unit formulations containing conventional non-toxic pharmaceutically acceptable carriers, adjuvants and vehicles. The term parenteral as used herein includes subcutaneous injections, intravenous, intramuscular, intrasternal injection or infusion techniques. In addition, there is provided a pharmaceutical formulation comprising a compound of general Formula I and a pharmaceutically acceptable carrier. One or more compounds of general Formula I may be present in association with one or more non-toxic pharmaceutically acceptable carriers and/or diluents and/or adjuvants and if desired other active ingredients. The pharmaceutical compositions containing compounds of general Formula I may be in a form suitable for oral use, for example, as tablets, troches, lozenges, aqueous or oily suspensions, dispersible powders or granules, emulsion, hard or soft capsules, or syrups or elixirs.
Compositions intended for oral use may be prepared according to any method known to the art for the manufacture of pharmaceutical compositions and such compositions may contain one or more agents selected from the group consisting of sweetening agents, flavoring agents, coloring agents and preserving agents in order to provide pharmaceutically elegant and palatable preparations. Tablets contain the active ingredient in admixture with non-toxic pharmaceutically acceptable excipients which are suitable for the manufacture of tablets. These excipients may be for example, inert diluents, such as calcium carbonate, sodium carbonate, lactose, calcium phosphate or sodium phosphate; granulating and disintegrating agents, for example, corn starch, or alginic acid; binding agents, for example starch, gelatin or acacia, and lubricating agents, for example, magnesium stearate, stearic acid or talc. The tablets may be uncoated or they may be coated by known techniques to delay disintegration and absorption in the gastrointestinal tract and thereby provide a sustained action over a longer period. For example, a time delay material such as glyceryl monostearate or glyceryl distearate may be employed.
Formulations for oral use may also be presented as hard gelatin capsules wherein the active ingredient is mixed with an inert solid diluent, for example, calcium carbonate, calcium phosphate or kaolin, or as soft gelatin capsules wherein the active ingredient is mixed with water or an oil medium, for example peanut oil, liquid paraffin or olive oil.
Aqueous suspensions contain the active materials in admixture with excipients suitable for the manufacture of aqueous suspensions. Such excipients are suspending agents, for example sodium carboxymethylcellulose, methylcellulose, hydropropylmethylcellulose, sodium alginate, polyvinylpyrrolidone, gum tragacanth and gum acacia; dispersing or wetting agents may be a naturally-occurring phosphatide, for example, lecithin, or condensation products of an alkylene oxide with fatty acids, for example polyoxyethylene stearate, or condensation products of ethylene oxide with long chain aliphatic alcohols, for example heptadecaethyleneoxycetanol, or condensation products of ethylene oxide with partial esters derived from fatty acids and a hexitol such as polyoxyethylene sorbitol monooleate, or condensation products of ethylene oxide with partial esters derived from fatty acids and hexitol anhydrides, for example polyethylene sorbitan monooleate. The aqueous suspensions may also contain one or more preservatives, for example ethyl, or n-propyl p-hydroxybenzoate, one or more coloring agents, one or more flavoring agents, and one or more sweetening agents, such as sucrose or saccharin.
Oily suspensions may be formulated by suspending the active ingredients in a vegetable oil, for example arachis oil, olive oil, sesame oil or coconut oil, or in a mineral oil such as liquid paraffin. The oily suspensions may contain a thickening agent, for example beeswax, hard paraffin or cetyl alcohol. Sweetening agents such as those set forth above, and flavoring agents may be added to provide palatable oral preparations. These compositions may be preserved by the addition of an anti-oxidant such as ascorbic acid.
Dispersible powders and granules suitable for preparation of an aqueous suspension by the addition of water provide the active ingredient in admixture with a dispersing or wetting agent, suspending agent and one or more preservatives. Suitable dispersing or wetting agents and suspending agents are exemplified by those already mentioned above. Additional excipients, for example sweetening, flavoring and coloring agents, may also be present.
Pharmaceutical compositions of the invention may also be in the form of oil-in-water emulsions. The oily phase may be a vegetable oil, for example olive oil or arachis oil, or a mineral oil, for example liquid paraffin or mixtures of these. Suitable emulsifying agents may be naturally-occurring gums, for example gum acacia or gum tragacanth, naturally-occurring phosphatides, for example soy bean, lecithin, and esters or partial esters derived from fatty acids and hexitol, anhydrides, for example sorbitan monooleate, and condensation products of the said partial esters with ethylene oxide, for example polyoxyethylene sorbitan monooleate. The emulsions may also contain sweetening and flavoring agents.
Syrups and elixirs may be formulated with sweetening agents, for example glycerol, propylene glycol, sorbitol or sucrose. Such formulations may also contain a demulcent, a preservative and flavoring and coloring agents. The pharmaceutical compositions may be in the form of a sterile injectable aqueous or oleaginous suspension. This suspension may be formulated according to the known art using those suitable dispersing or wetting agents and suspending agents which have been mentioned above. The sterile injectable preparation may also be sterile injectable solution or suspension in a non-toxic parentally acceptable diluent or solvent, for example as a solution in 1,3-butanediol. Among the acceptable vehicles and solvents that may be employed are water, Ringer""s solution and isotonic sodium chloride solution. In addition, sterile, fixed oils are conventionally employed as a solvent or suspending medium. For this purpose any bland fixed oil may be employed including synthetic mono- or diglycerides. In addition, fatty acids such as oleic acid find use in the preparation of injectables.
The compounds of general Formula I may also be administered in the form of suppositories for rectal administration of the drug. These compositions can be prepared by mixing the drug with a suitable non-irritating excipient which is solid at ordinary temperatures but liquid at the rectal temperature and will therefore melt in the rectum to release the drug. Such materials are cocoa butter and polyethylene glycols.
Compounds of general Formula I may be administered parenterally in a sterile medium. The drug, depending on the vehicle and concentration used, can either be suspended or dissolved in the vehicle. Advantageously, adjuvants such as local anesthetics, preservatives and buffering agents can be dissolved in the vehicle.
Dosage levels of the order of from about 0.1 mg to about 140 mg per kilogram of body weight per day are useful in the treatment of the above-indicated conditions (about 0.5 mg to about 7 g per patient per day). The amount of active ingredient that may be combined with the carrier materials to produce a single dosage form will vary depending upon the species of the host animal to be treated, the particular mode of administration, and the body weight of the host. Dosage unit forms will generally contain between from about 1 mg to about 500 mg of an active ingredient.
It will be understood, however, that the specific dose level for any particular patient will depend upon a variety of factors including the activity of the specific compound employed, the age, body weight, general health, sex, diet, time of administration, route of administration, and rate of excretion, drug combination and the severity of the particular disease undergoing therapy.
For administration to non-human animals, the composition may also be added to the animal feed or drinking water. It will be convenient to formulate these animal feed and drinking water compositions with a mullet-dose of the drug so that the animal takes in an appropriate quantity of the composition along with its diet. It will also be convenient to present the composition as a premix for addition to the feed or drinking water.
An illustration of the preparation of compounds of the present invention is given in Scheme I. 
In Scheme I, the substituents X and Y carry the definitions set forth above for formula I.